Jpn. J. Trop. Agr. 46 (2) :82-87, 2002

Fruit Ripening as Affected by Storage Temperature in White ( edulis Llave and Lex.)

Yoshimi YONEMOTO, Hirokazu HIGUCHI * and Yoshinobu KITANO * 2

Kihoku Branch, Tree Experiment Station, Wakayama Research Center of Agriculture, Forestry and Fisheries, Kokawa-cho Naga, Wakayama 649-6531, Japan * Graduate school of Agriculture Kyoto University, Oiwakecho, Kitashirakawa, Sakyou-ku, Kyoto 606-8502, Japan *2 Fruit Tree Experiment Station , Wakayama Research Center of Agriculture, Forestry and Fisheries, Kibi-choArida, Wakayama 643-0022, Japan

Abstract The time-course changes in respiration and ethylene production were investigated in •eYellow•f white sapote stored at 1, 5,10,15, 20, 25, 30 and 35 •Ž. Increase in the respiration rate coincided with that of ethylene production at 30 and 35 •Ž. However, the ethylene production rate increased after the increase in the respiration rate at 5-25 •Ž. Within 5 to 25 •Ž ranges, the respiration rate and ethylene production rate at the respective peaks were higher and the ethylene production peak occurred earlier than the respiration peak at higher temperatures. No ethylene production and a low respiration rate were induced during storage at 1 •Ž. The fruits became soft and edible at the time of peak ethylene production. The storage temperature did not affect the content of total soluble solids of the ripened fruits. Browning of the fruit skin was observed at 5 •Ž and above 30 •Ž, while browning did not occur under relatively warm conditions temperature ranging from 10 to 25 •Ž. At 5 •Ž, softening occurred only on the fruit surface, and the surface became water-soaked. All the fruits stored at 1 •Ž for 10, 20, 46 and 63 days could ripen after they were transferred to an environment at 25 •Ž. Since chilling injury occurred in the fruits stored for 63 days, it is suggested that the storage period could be extended to 46 days by storage at 1•Ž. Key words Ethylene production, Fruit ripening temperature, Fruit skin color, Fruit storage, Respiration

貯 蔵 温 度 が シ ロサ ポ テ(Casimiroa edulis Llave and Lex.)果 実 の追 熟 に及 ぼ す 影 響 米 本仁 巳 ・樋 口 浩 和*・ 北 野 欣 信*2和 歌 山 県 農 林水 産 総 合 技 術 セ ン タ ー果 樹 園 芸 試 験 場紀 北 分場 〒649-6531和 歌 山 県 那 賀郡 粉河 町粉 河*京 都 大 学 大 学 院 農学 研 究 科 〒606-8502京 都 市 左 京 区北 白川 追 分 町*2和 歌 山県 農 林 水 産総 合 技 術 セ ン ター果 樹 園芸 試 験場 〒643-0022和 歌 山 県有 田郡 吉備 町奥

要 約 シ ロサ ポ テ‘Yellow’の 果 実 を用 い て,1,5,10,15,20,25,30お よ び35℃ で の 貯 蔵 が果 実 の 呼 吸 お よび エ チ レ ン生 成 に 及 ぼ す影 響 を調 査 し た.5～25℃ で は,エ チ レ ン生 成 の増 加 は 呼 吸 の ク ラ イ マ ク テ リ ッ ク ラ イズ の 後 で あ っ た が,30℃ と35℃ で は両 者 が ほ ぼ 同 時 に起 こ っ た.5～25℃ で は温 度 が高 い ほ ど ピー ク時 の 呼 吸 量 が 高 く,エ チ レ ン生 成 の ピー ク まで の 期 間 は短 く, 生 成 量 も高 か っ た.1℃ で は エ チ レ ン の生 成 は み られ ず,呼 吸 量 は低 く推 移 し た. 果 実 は エ チ レ ン生 成 の ピ ー ク 時 に軟 化 し,食 べ 頃 と な っ た.貯 蔵 温 度 は可 溶 性 固形 物 含 量 に影 響 し な か っ た.果 皮 の 褐 変 が5℃ と 30℃ 以 上 で 発 生 した.5℃ で は 果 実 表 面 に近 い部 分 の み 軟 化 し,果 皮 は 水浸 状 と な っ た.1℃ で10,20,46お よ び63日 間貯 蔵 し た後 に25℃ に移 した と こ ろ,全 て の 果 実 で 追 熟 し た が,63日 間 の貯 蔵 で は 低 温 障 害 が 発 生 した.シ ロ サ ポ テ で は1℃ で46日 間 貯 蔵 で き る こ とが 示 唆 され た. キ ー ワ ー ド エ チ レ ン生 成,果 実 追 熟 温 度,果 実 貯 蔵,果 皮 色,呼 吸

over longer distances. However, methods to Introduction prevent the softening of the white sapote fruit white sapote, indigenous to central Mexico9), have not been developed yet. has been grown in the northern part of South BIALE et al.3) reported that the white sapote America and the West Indies. It grows well fruit shows a respiratory •eclimacteric•f peak under sub-tropical conditions but can also grow (carbon dioxide output) after harvest. However, in warm regions of the temperate zone8,10,12,14) little information is available on the post harvest The fruit is sweet and delicious, but the shelf life life. The relationship between the storage is very short because of quick softening. temperature and fruit ripening has been investi- Furthermore, the peel of the fruit is prone to gated for many tropical and sub-tropical fruits1,3,4) bruising2,5,11). In recent years, advanced storage However, the effect of the storage temperature systems have enabled to transport fresh fruits on the ripening behavior is poorly documented. The objective of this study was to identify Received Jul. 31, 2001 Accepted Feb. 15, 2002 the physiological characteristics of ripening in YONEMOTOet al.: Postharvest Physiology of White Sapote 83

white sapote fruits exposed to different storage independently evaluated the taste as poor, fair,

temperatures. In particular, the changes in the good or very good. The degree of peel browning ethylene production and respiration rates, the was categorized as zero, light, moderate or rate of softening and color development of the severe. The fruits were weighed when the fruits were investigated. ethylene production rate was measured. The

Materials and Methods percentage of weight loss for each fruit was calculated by dividing the•gweight loss since Experiment 1 harvest•h by the •ginitial weight at harvest•h. . The fruits used in this experiment were obtained from four-year-old container-grown Experiment 2. •e Yellow•f trees. Trees were grown in a greenhouse Another 12 fruits which did not produce at Wakayama Fruit Tree Experiment Station in ethylene were selected for this experiment on Japan. Since this cultivar does not produce July 31. Three fruits were stored at 1 •Ž for 10, pollen18), the flowers were pollinated with fresh 20, 46 or 63days by the same method as that pollen of •eVernon•f, from the end of March through applied in experiment 1. All the fruits became early April. Fruits were harvested on July 31. ripe at 25 •Ž after the end of the respective Ethylene production and respiration rates were storage treatments. Respiration and ethylene

measured individually at room temperature production rates were measured during storage (approximately 25 •Ž) immediately after the and the ripening period. The measurements harvest by gas chromatography as described were conducted every day during the ripening

below. Fruits that did not produce ethylene period to determine the ethylene production were selected and incubated at 5, 10, 15, 20, 25, peak. Skin color was determined at harvest, at 30 or 35 •Ž. To prevent excessive drying, each the end of the 1 •Ž storage treatment and every fruit was placed individually in a polyethylene day during the ripening period. Fruit weight at bag (0.02mm thickness) and the bags were left the end of the 1 •Ž storage period and the unsealed with only the upper portion of the bags ethylene production peak was measured to folded so as to permit ventilation. Three fruits calculate the percentage of fruit weight loss. were used for each treatment. The respiration The content of TSS in the juice, degree of peel rate (carbon dioxide production) and ethylene browning or eating quality were determined or production rate were measured every two days categorized by the same methods as those for every treatment. Each fruit was sealed in a applied in Experiment 1. 4.1 litre acryl chamber and kept at the same Results temperatures as those under the storage conditions for one hour. Ethylene and carbon Experiment 1. dioxide concentrations in the head space of the Carbon dioxide production was higher at acryl chamber were measured using FID and higher temperatures (Fig. 1). The respiratory TCD gas chromatograph systems (GC-17A and climacteric peak was observed on the fourth GC-14BPT, Shimadzu Co. Ltd.), respectively. day after the fruits were stored at 35 °C and on Stainless columns 2m long, filled with Porapak the sixth day after storage at 15, 20, 25 and 30 Type-9, were used, and the column tempera- •Ž. Fruits stored below 10 •Ž did not show a tures were 70 •Ž and 50 •Ž for the detection of distinct respiration peak. The peak of ethylene

ethylene and carbon dioxide, respectively. After production occurred earlier and the amount of the measurements, the firmness of the fruit was ethylene produced increased with the increase assessed by touching the fruit, and each fruit in the storage temperature (Fig. 1). There was was put back into the bag and stored at the no significant difference in the rate of ethylene

same temperatures. Skin color was determined production at the peak among 25, 30 and 35 •Ž. daily for the fruits stored at 25•Ž and 35•Ž. The The ethylene production peak was not distinct at a*, b* and L values were determined with a 5•Ž. colorimeter (CR 200b, Minolta Co., Ltd.). When Storage temperature affected the fruit quality

a fruit became soft, the content of total soluble (Table 1). Fruit ripening occurred normally at solids (TSS) in the juice was measured with a 15, 20 and 25•Ž. The content of TSS was relatively refractometer. For the organoleptic test, 5 persons low at 5 •Ž, but not appreciably different among 84 Jpn. J. Trop. Agr. 46 (2) 2002 the storage temperatures above 10 •Ž. Only the Skin color index a* increased markedly after surface became soft and showed a water-soaked harvest, whereas the b* value increased only appearance in the fruits stored at 5 •Ž. Peel slightly and the L value did not change during browning occurred at 5, 30 and 35 •Ž. The the ripening period (Fig.2). The level of a* highest eating quality was observed in the fruits stored at 15-25 •Ž but the quality was fair in the fruits stored at 10 •Ž or above 30•Ž.

Fig. 1. Time course changes in A) carbon dioxide Fig. 2. Time course changes in fruit skin color A)

and B) ethylene production rates in white a*, B)b* and C) L values of white sapote

sapote •eYellow•f fruit as affected by storage •e Yellow•f fruit during storage at 25•Ž and 35•Ž.

temperatures. Vertical bars indicate SE. (n=3).

Vertical bars indicate SE. (n=3).

Table 1. Effect of ripening temperature on fruit weight loss and content of total soluble solids (TSS) of white sapote •eYellow•f fruit.

Velues are average •} SD (n=3). * : Values in parenthesis denote the fruit weight loss percentage when the fruit became soft . *2: Degree of peel browning was evaluated based on four grades: no browning , light, moderate, and severe browning. *3: Eating quality was evaluated based on five grades: very good , good, fair, poor and not edible. YONEMOTO et al.: Postharvest Physiology of White Sapote 85 became higher at 35 •Ž than at 25 •Ž. Fruit skin storage as compared with 2 days for the 63-day color after ripening was pale yellow at 25 •Ž and storage. There were no significant differences in ocher or brown at 35 •Ž. the peak of the respiration rate among the storage periods (Fig. 3). The number of days to Experiment 2. the ethylene production peak also decreased as All the fruits were able to ripen at 25•Ž after the storage period increased (Fig. 3). The ethylene storage for 10, 20, 46 and 63 days at 1 •Ž. The production peak was observed on the seventh time required to reach the respiratory climacteric day during the ripening after 10- and 20-day peak became shorter as the storage period storage at 1 •Ž, and it was observed on the increased (Fig. 3). It took 6 days for the 10-day fourth and second days after 46-and 63-day storage at 1 •Ž, respectively. The increase in the rate of ethylene production followed the increase in the respiration rate. No ethylene production was observed during the storage at 1 •Ž for 63 days. The fruit was firm and the skin color remained yellow-green during the 1 •Ž storage. In the fruits stored for less than 20 days, the fruit skin color was pale yellow after ripening. The skin color became ocher in the fruits stored for 46 days and ocher or brown in the fruits stored for 63 days (Table 2). The skin color index a* remained at the same level during the 1 •Ž storage period (Fig. 4). Index a* increased during the ripening period at 25 •Ž. As the 1 •Ž storage period increased, the increase in the level of a* was higher during the ripening stage. In the fruits stored for less than 46 days, b* showed the same level during the ripening

period, but the level decreased in the fruits stored for 63 days. The content of TSS after ripening at 25 •Ž was not affected by the storage

period. The taste of the fruits stored for 63 days Fig. 3. Time course changes in A) carbon dioxide was slightly poorer.

and B) ethylene production rates in white Discussion sapote •eYellow•f fruit during ripening at 25 •Ž after various storage periods at 1•Ž. The results obtained in this study indicate Vertical bars indicate SE. (n=3). that the suitable temperatures for fruit ripening

Table 2. Effect of extended storage at 1•Ž on fruit weight loss and content of total soluble solids (TSS) of white

sapote •eYellow•f fruit.

Velues are average •} SD (n=3). * : Degree of peel browning was evaluated based on four grades: no browning , light, moderate, and severe. * 2: Eating quality was evaluated based on five grades: very good , good, fair, poor and not edible. Fruits ripened at 25•Ž after various periods of storage at 1•Ž. 86 Jpn. J. Trop. Agr. 46 (2) 2002

period was much longer at 1 •Ž than at 5 •Ž. No ethylene production was observed in the fruits during storage at 1 •Ž for 63 days, and these fruits ripened normally with a clear peak of ethylene production at 25 •Ž. After a 46-day storage period at 1 •Ž, •eYellow•f fruits ripened normally at 25 •Ž but fruits stored for 63 days experienced severe peel browning and showed a low eating quality. The white sapote may have experienced a chilling injury after 46 days to 63 days of storage at 1 •Ž. It is recommended that the storage period should not exceed 46 days. In conclusion, the optimum ripening tempera- tures in white sapote fruit ranged between 15 •Ž and 25 •Ž. Extended storage for 46 days was achieved at 1•Ž. However, further investigations are required for extending the storage period while avoiding the browning of the fruit skin.

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